Nervous System

Honors BiologyPowerpoint #3Unit 8 – Chapter 35 pg. 897-904

The Senses Activities

Function of Nervous System:

Coordinates the body’s response to changes in its internal and external environments.

NeuronsMessages carried by nervous system are electrical impulses

Cells that transmit impulses are called NEURONS

3 types of neurons:1. Sensory: carry impulse from sense organ to

spinal chord and brain2. Motor: carry impulse from brain and spinal

chord to muscles and glands3. Interneurons: connect sensory and motor and

carry impulses in between

Neurons

Pyramidal neurons forming a network in the brain

Neurons: Structure

• Cell Body (Soma): Cell’s “life support” center

• Dendrites - conducts “signal” toward the cell body -- [input zone]• Receives signal from sensory cell or neighboring neuron

Axon - usually a single fiber -- [conducting zone]conducts signal away from cell body to another neuron or

effector cell

Axon Ending- a cluster of branches (100’s to 1000’s) that relays signal to next neuron / effector cell

Myelin SheathCovers the axon of some neurons Allows signal to travel faster because impulse “jumps” from node of Ranvier to node of Ranvier (with myelin sheath (225 mph / without 11 mph)

Multiple Sclerosis• Immune System attacks Myelin in brain and spinal

chord

Multiple Sclerosis (MS)• Loss of motor functions

1) At Rest - The neuron is POLARIZED (-70mV)There is a slightly negative charge on the inside, and a positive charge on the outside….. Why?

balance is maintained by the sodium-potassium pump (active transport)

Pumps Na+ (sodium) outside & Pumps K+ (potassium) inside Membrane leaks and some K+ goes back out Resting Potential= -70mV because overall postive charge outside

and negative charge inside

How a nerve impulse is transmitted

2) Depolarization Stimulus causes opening of Na+ gates, allowing

Na+ to rush in (facilitated diffusion) changes the neuron from polarized to de-polarized

then to + 30mV Reversal of charges = Nerve impulse aka Action

Potential

How a nerve impulse is transmitted

2) Depolarization

This is all-or-none, meaning a stimulus must exceed a threshold for the action potential to occur

Intensity of the stimulus is based on the number of neurons that exhibit an action potential.

Speed of impulse based on diameter of axon & amount of myelination.

How a nerve impulse is transmitted

3) Repolarization After inside flooded with NA+, K+ gates open and

let K+ out (while NA+ gates close) The inside becomes –while outside become + and

this repolarizes membrane

How a nerve impulse is transmitted

How a nerve impulse is transmitted4) Refractory period When the Na+/K+ balance returns to

normal (K+ on inside and Na+ outside) During this time the neuron will not respond to

new impulses

Nerve Impulse Transmission

The Synapse•Neurons DON’T touch•The gap between the axon of one neuron, and the dendrites of another is called the SYNAPSE

1. Action potential happens2. Neurotransmitter is released by axon ending

Neurotransmitter is a chemical that sends a signal3. Neurotransmitter binds to dendrite

membrane of next neuron4. Excitation or inhibition of the membrane

occurs5. Neurotransmitter is ‘recycled’

The Synapse

Divisions of the Nervous System:

1. Central Nervous System (CNS)

2. Peripheral Nervous system (PNS)

1. The Central Nervous System (CNS)Relays messages, processes information and analyzes information.

Includes:BrainSpinal Cord

Parts of the BrainCerebrum’s Purpose: Controls voluntary activities of the bodyCite of intelligence, learning, and judgmentMade up of frontal, parietal, occipital, and temporal lobes

Phineus Gage

Parts of the brainCerebellum: coordination and balance

Brain stem: regulates blood pressure, heart rate, breathing, and swallowing

Parts of BrainThalamus: relays sensory input to proper region of cerebrum

Hypothalamus: control center for recognition and analysis of hunger, thirst, fatigue, anger, and body temperature

2. Peripheral Nervous System: everything outside of CNS

1. Sensory Division: transmits impulses from sense organs to central nervous system

What are sense organs? Organs designed to pick up stimuli (name 5 sense organs)

2. Motor Division: Transmits impulses from CNS to the muscles or glands

Quick Quiz: Which is sensory which is motor?Seeing Raising your handTastingBlinking when a ball is thrown past your face

Sensory

Sensory

Sensory when you see the ball, motor when you blink

Motor

Motor Division of PNS2 parts

1.Somatic Nervous systemRegulates activities under conscious control (ex. Moving

skeletal muscles)Some involved with reflexes and can act without

conscious control (see next slide)

2. Autonomic Nervous SystemRegulates activities that are automatic or involuntaryExample: when running, speeds up heart and blood

flow, stimulates sweat glands and slows down digestionDivided into sympathetic and parasympathetic

Reflex Arc

Sensory neuron interneuron motor neuron Without brain processing

Reflex Arc

Parkinson’s Disease

CauseParkinson's disease is a disorder of the brain that leads to shaking (tremors) and difficulty with walking, movement, and coordination.

Caused by loss of dopamine producing cells in brain (substantia niagra)

Dopamine helps control muscle movement by releasing inhibitory function of substantia niagra so things are not moving when not specifically told to do so

Without dopamine, it takes more effort for each motion and movements are shaky

DON’T DO DRUGS!!!!!